1. Field of the Invention
The present invention predominately relates to flexographic printing processes. More particularly, the invention relates to a process for uniformly applying a water-based color coating or ink to the entire surface area of a paper web side which represents the material supply for a converting apparatus such as an envelope machine.
2. Description of the Prior Art
Large numbers of stationery users require or desire colored envelopes and/or letter sized paper. For standardized colors, sizes and shapes, colored stationary needs are met with colored paper in which the colorant is blended with the paper stock before a web therefrom is laid on a papermachine. By this process, economics require large orders and inventories of a given paper color.
Small orders of uniquely colored envelopes are particularly difficult to meet, economically. Traditionally, such envelopes have been manufactured from white, substantially uncoated paper by a process which includes a flexographic print coating of the envelope machine supply web with a coating of solvent based ink: except in those areas where the envelope gum or adhesive is to be applied. This exception was necessary to accommodate the fact that the usual non-toxic envelope gums will not adhere to solvent ink coated surfaces.
Notwithstanding the gum adherence difficulty with solvent ink, water-based inks have not been used in these applications due to the curling consequences of water-based ink upon the web. Envelope machines are extremely critical with requirements of a flat, uniform web surface. Excess water vehicle absorbed by the web from the prior art water-based inks made the supply web warp, wave and curl.